Conventional peripheral alarm detection devices used in the detection of smoke or fire have a head component for sensing the presence or absence of smoke or fire, and a base component in electrical communication with both the head component and a central control panel. The head component generates an analog value representative of an alarm condition. The value is outputted to the base component. The base component converts the analog signal to a digital one, and sends the converted signal to the control panel. The control panel, using a predetermined algorithm inserts the received signals into an algorithm and then evaluates whether an alarm condition exists and acts on it.
Generally, the head component in a peripheral smoke or fire detection device is a smoke sensor or heat detector. Conventional smoke and heat detectors are categorized as ionization, photo-optical and heat sensors. Usually, these sensors comprise sampling chambers in which an ambient condition is converted to a direct current voltage. Typically, the head component in fire detection systems becomes dirty with age and exposure to combustion products, dust and other film-forming contaminants. When a head component becomes dirty, the sensitivity of the head component is jeopardized and the level of protection provided is lessened. Thus, the head component must be removed and cleaned where possible, or replaced if defective.
Ionization, photo-optical and heat sensors have unique operating and analog output characteristics requiring different algorithms or values to be inserted into an algorithm to correctly evaluate the output of the sensors. For example, addressable interface Model No. 4100-8301 manufactured by Simplex Time Recorder Co. is a control panel in which a moving average of each peripheral fire detection device's output is maintained by the control panel. In such a control panel an alarm condition is determined by comparing the current value of the output of a peripheral fire detection device to the average value maintained by the control panel. Because each type of head component has a different analog value output, each produces a different average value. Accordingly, it is imperative that the control panel recognize the particular type of head component installed at the peripheral device so the correct average associated with the head component is applied to determine the presence or absence of an alarm condition.
In conventional addressable fire detection systems, the address representing the location of a given peripheral device is a predetermined digital value stored within the head component. Therefore, if a head component is removed from a base component at a first location and reinstalled into a base component at a second location, the address received by the control panel remains the same even though the location of the head component has changed.
In addition, in conventional alarm systems moving a head component of one type to a second location, where a different type of head component is desired, becomes problematic. For example, if a heat sensor is installed at a location where smoke is likely to be the predominant sign of a fire, such as a smoldering fire, safety could be compromised, because a photo-optical sensor is better suited for such a location. In an exchangeable head system, if the control panel cannot determine what type of sensor is installed at a particular location, the control panel may apply an incorrect algorithm or values to the data received from the peripheral device, resulting in false, missed or delayed alarms.
In the past, it has been necessary to provide as many as seven connection ports or pins between the head and base components to provide adequate means for communicating data and analog values between the head and base components. If the head component of a peripheral device can be one of several different types, it is necessary that each type of head component (typically three types) have its own connection port or pin. Then, there is one connection port or pin over which a sample command is communicated, two connection pins or ports over which the information corresponding to the sample is sent back to the base component and two power connection ports or pins, for a total of seven connection ports or pins.
In view of the deficiencies and inefficiencies of the prior art, it is desirable to have a simplified peripheral fire detection system with improved reliability having peripheral devices which communicate with a control panel to indicate when and what type of head component is connected to the base. It is also desirable to indicate if the type of head installed at a particular location has been changed to avoid improper processing.